Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface in a first embodiment showing my new design;

FIG. 2 is a front view of a display screen or portion thereof with a graphical user interface in a second embodiment shown on a smartphone;

FIG. 3 is a back view thereof;

FIG. 4 is a right-hand side view thereof;

FIG. 5 is a left-hand side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines showing a smartphone represent environment and form no part of the claimed design. The remainder of the broken lines shows portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or a portion thereof with a graphical user interface, as shown and described. 